The present invention relates to a disc brake including an improved construction for mounting friction pad assemblies.
There has been and is now widely used a disc brake of the type in which a pair of friction pad assemblies being supported by a non-rotating member are forced against both sides of a rotating disc upon brake application. In the disc brake of such type, each of the friction pad assemblies is required to be slidably mounted on or received in the supporting member so that the pad assembly is free to move inward and outward in an axial direction along a line normal to the sides of the disc rotor. One of the typical structures for attaining this purpose has been to provide the supporting member itself with guide or abutment surfaces or ways on and along which the pad assemblies slide toward and away from the disc rotor.
It has been found, however, that such type structure of disc brake is not completely satisfactory because of the disadvantage that the pad assembly may rattle, especially when the brake is installed on automotive vehicles or other equipment involving high-frequency vibrations during operation. One solution that has been attempted to this rattling problem of the pad assembly, is to interpose an elastic material between the pad assembly and corresponding surfaces of the supporting member so that an elastic force is exerted onto the pad assembly in one given direction parallel to the friction surfaces of the pad and disc, thereby letting the pad assembly vibrate together with its supporting member as a unit. Any elastic material that may serve such a function is generally referred to as an anti-rattle spring.
Furthermore, such type of disc brake has still another disadvantage that the abutment surfaces of the pad assembly and its supporting member are easy to corrode or rust and may even stick together under certain conditions. The rusty or sticky condition of the abutment surfaces is a possible source that prevents a normal and smooth braking action. Even an extremely slight degree of rust produced on the abutment surfaces of the pad assembly and the supporting member may hinder the pad assembly from retracting to its normal position away from the disc rotor for a needed running clearance upon releasing brakes, or may cause a so-called "brake drag" complaint. Accordingly, every possible and strenuous effort has been made so far to find a solution to this brake dragging problem which may not only inflict an extra load to a vehicle engine and consequently increase the fuel cost but also induce very serious and hazardous conditions of the brake such as overheating and vapor-lock.
And what is worse, when the abutment surfaces are heavily rusted, more brake pedal pressure is needed for initial braking effect and in the worst case, the friction pad assembly may stick to its supporting member and thus fail to slide axially, thereby putting the brake in critical conditions.
The present invention has the background as described hereinbefore.